Country of Birth is the highest risk factor associated with the development of insulin dependent diabetes mellitus (IDDM). However, the relative contributions of the environment and the genetics of the population to this risk are unknown. The Caribbean Basin offers a unique opportunity to study the genetic and epidemiological aspects of IDDM for the following reasons: there is a marked difference in the incidence rates of the islands varying from 2/ 10[5]/ yr in Cuba to 12/10[5]/yr in Puerto Rico; the islands are geographically separated; and the ancestry of each island population is defined. In addition, cohorts of Caribbean Basin islanders have migrated to the continental United States within the last two generations. The extended objective of our research is to describe the epidemiology of IDDM in Puerto Rico for comparison to other populations in the Caribbean and worldwide. We will further the accomplishment of this objective by (1) the surveillance of IDDM incidence on the island via the PSM/MBRS IDDM registry , (2) the characterization the MHC Class I and II gene regions in the IDDM population, their families, and controls, (3) the determination of the risk of NIDDM and IDDM to family members of IDDM children; and (4) the comparison of the incidence rates of PB IDDMs and a migrant population of PR-heritage IDDMs in the US mainland. We will compare our data to other populations via DIAMOND, the WHO's multinational project for childhood diabetes. Accomplishment of these goals will afford students the opportunity to participate in two types of research: the technology of HLA determination by serological and DNA methodology, and epidemiological investigations.